High-frequency directed radio energy system



Nov. 17, 1953 v B. M. TORREY 2,659,818

HIGHjFREQUENCY DIRECTED RADIO ENERGY SYSQM Filed July 21, 195o PatentedNov. 17, 1953 HIGH-FREQUENCY DIRECTED RADIO ENERGY SYSTEM Bradford M.Torrey, Milton, Mass., assignor'to Raytheon Manufacturing Company,`Newton, Mass., a corporation of Massachusetts Application July 21, 1950,Serial No. 175,153"v 1 claim. (o1. 250533.65)

This invention relates to the use of lenses for directing radio-energyradiations of radar sysstems in streamlined bodies.

Radar equipment in airborne installations has, in the past, required theuse of radomes for protection from wind and other weather conditions.The necessarily bulky nature of radomes has many objectionable features.Besides radiation losses and beam distortion caused bythe radome duringscanning, another very important objection is the undesirableaero-dynamic drag. The radome protuberance from the streamlined surfaceof, for example, a military plane upsets the streamlined flow and causesconsiderable reduction in the speed attainable.

Pursuant to the present invention, the objections of radome structuresare overcome and directional radar installations may be made instreamlined equipment without impairing the drag characteristics. needfor a conventional radome with its resultant losses and distortionsduring scanning, the need for a parabolic reiector, as is usually usedfor obtaining a radar beam, is also eliminated. These, and otheradvantages, are achieved in the present invention by using a lens ofdielectric material, such as polystyrene, as the directive beam-formingelement in the system. The external surface of the lens may be made toapproximate the proper streamlined curves of the streamlined body. Byproper shaping of the inside surface of the lens in accordance withconventional trigonometric trace principles in lens design, compensationfor the external curvature may be effected and a suitable beam ofradiated energy from the radar system produced. In such an arrangement,proper scanning may be obtained by moving the radar horn or antenna withrespect to the center line of the lens and the lens may remainstationary.

A present embodiment of the invention incorporates the above in aconstruction particularly adapted to highly streamlined Vehicles, suchas :iet-propelled aircraft. ln this embodiment, a lens is placed in thenose of the aircraft and mounted so that the outside contour of the lensblends with the contour of the streamlined surface of the plane. Aconventional radar apparatus in the plane is arranged with its antennaor horn at the focal point of the lens. The antenna is made to move onsuitable tracks about the center of the lens, thereby providing forscanning by changing the position of the antenna. Thus the lens not onlytakes the place of the conventional parabolic reflector providingBesides eliminating the lens;

Fig. 3 is a graph illustrating a beam obtainable in the invention; and

Fig. 4 is a graph illustrating the illumination of the lens forobtaining the beam pattern in Fig. 3.

Referring to Fig. 1 in more detail, streamlined surface Il) in the frontend I2 of 'a jet-fighter plane has integrally mounted therein a lens iiiof suitable material, such as polystyrene, transpattern parent to highfrequency radio energy, and having an outside contour I6 blending Withthe streamlined surface Il). The inside surface I8 of the lens isprovided with a contour arrived at through the use of geometric opticsand raytracing, such that, together with the outside contour I6, anarrow beam 20 of radio energy is formed when an antenna or horn 22connected through a flexible wave guide 24 to a conventional radarsystem 26 radiates energy at the focal point 28 of the lens I4. In thepresent embodiment, polystyrene with an index of refraction of 2.43 wasused in plano-convex lens having a 7 diameter and a 61/2" focal lengthand was found suitable for use with a radar system 26 operating at afrequency of 24,000 megacycles. An exemplary beam pattern obtained bythis arrangement in the horizontal plane is shown by curve 2l in Fig. 3.This beam pattern was obtained by an illumination pattern over the lensin the same plane as shown by curve it in Fig. 4. Other types of lenses,however, such as double-convex or concave-convex design to obtaindesired frontal curve I6, which may be other than spherical, may also befound to produce a suitable beam pattern 2o.

The horn 22 is fixed, as by a support 29, to a block 30, arranged toslide on tracks 32 in a vertical plane. The tracks 32 have a contoursuch that the horn 22 will travel in a path about the center 34 of lensI4 which produces least aberration in lens l in forming the beam 20. Thetracks 32 are mounted securely, as by supports 36, to a block 38,arranged to slide on tracks 40 in a horizontal plane. The tracks El alsohave a contour such that the antenna 22 will be made to travel about thecenter 34 of lens i4 in a path producing least aberration from lens lllto the beam 20. A motor and reducing gear 42, controlled through lineslili from a suitable control source, not shown, may be used to drive theblock 38 by a pulley 45 in contact with one of the guides lli! andthereby antenna 22 along the horizontal path determined by the guidesfill. In similar manner, a motor and reducing gear 8 controlled throughlines 50 may be used to drive a pulley 52 in contact with one of theguides 32 to move the horn 22 in a Vertical plane. The horn 22 ispreferably directed at all times toward the center 34 of lens lli. Inthis manner, suitable scanning may be obtained up to 30 degrees in anydirection from the center line 54 of the lens Ill Without seriousdeterioration of the pattern of beam 20 due to limitations in the lensI4.

While a lens l, may be used in a system operating below 24,000inegacycles, the necessary increase in dimensions of the lens requiredby the increased Wave length of suc-n lower frequency energy makes itpreferable to conne such lens applications to systems operating above20,606 megacycles.

To assist in proper illuminaticn of the lens and thereby preventundesirable side lobe effects, the inside of the streamline surface H3and other reflecting surfaces may be coated with a radiationabsorbingsubstance, such as carb-on or nely divided iron particles.

This invention is not limited to the partici details of construction,materials and procet described, as many equivalents will suggest t e'selves to those skilled in the art. It is accord. desired that theappended claim be given broad interpretation commensurate with the scopeo the invention within the art.

What is claimed is:

' system comprising: a vehicle hos.

. wall provided with a streamline surface; a

o; dielectric material c-' ristitutingof f ll; the curvature of onesurface of said @cope-rating with said first-named cui le said lens witha predetermined g characteristic; a directive radioquency energyradiating horn mounted in e substantially at the effective focal n x inelement in selected planes aber-it the center lens.

BRADFORD M. TORRE?.

